[Navigation Experiment] Add WKBasedNavigationManagerImpl.

ios/web/navigation/navigation_manager_delegate.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_DELEGATE_H_
 #define IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_DELEGATE_H_
 
 #include <stddef.h>
 
 #import "ios/web/public/navigation_manager.h"
 
 namespace web {
 
 struct LoadCommittedDetails;
 class WebState;
+class WebViewNavigationProxy;
 
 // Delegate for NavigationManager to hand off parts of the navigation flow.
 class NavigationManagerDelegate {
  public:
   virtual ~NavigationManagerDelegate() {}
 
   // Instructs the delegate to begin navigating to the item with index.
   // TODO(crbug.com/661316): Remove this method once all navigation code is
   // moved to NavigationManagerImpl.
   virtual void GoToIndex(int index) = 0;
 
   // Instructs the delegate to load the URL.
   virtual void LoadURLWithParams(const NavigationManager::WebLoadParams&) = 0;
 
   // Instructs the delegate to reload.
   virtual void Reload() = 0;
 
   // Informs the delegate that committed navigation items have been pruned.
   virtual void OnNavigationItemsPruned(size_t pruned_item_count) = 0;
 
   // Informs the delegate that a navigation item has been changed.
   virtual void OnNavigationItemChanged() = 0;
 
   // Informs the delegate that a navigation item has been commited.
   virtual void OnNavigationItemCommitted(
       const LoadCommittedDetails& load_details) = 0;
 
   // Returns the WebState associated with this delegate.
   virtual WebState* GetWebState() = 0;
+
+  // Returns the main WKWebView used to display web content.

[Eugene But (OOO till 7-30), 2017/06/29 01:48:19]

Update comment?

[danyao, 2017/06/29 16:05:25]

Done.

+  virtual WebViewNavigationProxy* GetWebViewNavigationProxy() const = 0;
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_NAVIGATION_NAVIGATION_MANAGER_DELEGATE_H_